Dynamo-electric machine or motor



(No Model.)

E. THOMSON.

DYNAMO ELECTRIC MACHINE 0R MOTOR.

Patented Sept. 13, 1887.

WITNESSES A TTOHNE YS Therefore a UNITED STATES PATENT OFFICE.

ELIHU THOMSON, OF LYNN, MASSACHUSETTS.

DYNAMO-ELECTRIC MACHiNE OR MOTOR.

SPECIFICATION forming part of Letters Patent No. 869,754, dated September 13, 1887.

Serial No. 232,943. (No model.)

To all whom, it may concern:

Be it known that I, ELIHU THOMSON, a citizen of the United States, and a resident of Lynn, in the county of Essex and State of Massachusetts, have invented certain new and useful DynamoElectric Machines or Motors, of which the following is a specification.

My invention relates to the construction of dynamo-electricmachines and motors designed for use in supplying current to are lights or other working-resistances in series under conditions where there is a liability to variations of the main-line resistance, or for use as motors on circuits Where the currents supplied to the motor are variable, butit is desired to main tain, notwithstanding, an approximately constant speed in the motor.

My invention is primarily intended'for application to machines used as generators, and I shall hereinafter describe my invention with reference to such use of the machine.

The application of the invention to a motor will be obvious from the suhjoined description of its application to a generator.

' Dynamo-machines employed in running are lights in series must possess peculiar properties in order to insure stability of current and freedom from oscillation. This is due to the fact that when the current increases in an are its resistance diminishes, and vice versa. machine whose elcctro'motive force is sustained or increased when its current is increased by a momentary fall of resistance in the circuit will give rise to a further current increase,only limited by the separating power of the arc lamp mechanism in opening the arcs; but this latter action of compensation is too sluggish and behind time, and the general result has been that oscillations of periodic frequency are set up in the current and in the ares. It has generally been found necessary to limit the iron used in the machine, and so proportion its field strength relatively to the magnetism of the armature that the condition as above stated is avoided; but such limitations are usually made at a sacrifice of efiiciency and general output for a given weight.

My invention has for its object to provide means whereby there may be a large amount of iron used in the construction of the machine, a relatively small amount of copper, and to confer the property of yielding a lower electro-motive force 'when the current surpasses the normal. other armature arrangements may be used, and the armature may contain a much larger amount of iron relatively to the wire than in are machines as ordinarily constructed.

The field-magnet I construct so that a part thereof shall be magnetized to full saturation by the current of the machine or by another current; or a permanent field-magnet may be employed. The other part I construct with much heavier iron core and with a very small number of turns of wire in which the current flows, which current maguetizes, or, rather, tends to magnetize, the magnet-core iuopposition to the magnetism induced in it from the induction of the saturated or permanent part.

In the accompanying drawings, Figure l is a side elevation of a machine embodying my invention. Fig. 2 illustrates in detail the principle of the invention. Fig. 3is a diagram illustrating a modification. Fig. 4 isa diagram illustrating a modification in the connection of the two coils. Fig. 5 shows a form of fieldmagnet that may be employed for facilitating the action. Fig. 6 illustrates another form of the invention. Figs. 7, 8. and 9 are diagrams explanatory of the effects produced upon the electro-motive force of the machine. Fig. 10 illustrates a further modification ot' theinvention.

In Fig. 1, A is the armature of the Siemens or Gramme type or other form; K, the corn mutator; B B, the brushes bearing thereon at neutral line.

F is the coil on a field-core of moderate section. The coil F, which may be a maincircuit or other coil, energizes the core to saturation, being suitably proportioned as to convolutions with the normal current. Its pole N is thereby given a strong polarity opposite the armature. Many convolutions of wire in F are required. The coil M is either coarser than F or at least has much fewer turnssay one-fifth those in F-or its magnetizing effect is much lessfor instance, as one-fifth that of F; but the core of M is of large body and is far below saturation. The current in M,which is in the main circuit, is in a direction oppos ing that in F, or tending to make apole at the pole-face N of the same name as F makes at N. In reality, however, the strong induction from N through the armature A overcomes this tendency and forces N to assume an opposite polarity to N.

Siemens. Gramme, or

L represents a series of lights, as are lamps.

Fig. 2 shows the relation of parts and direction of winding of the field-coils.

Fig. 3 shows that F may be excited from a separate source.

Fig. 4: shows that F and M may, if suitably wound, be connected in multiple. In this case coil M is of much higher resistancesay five times Fand is of so few turns that it still has, say, one-fifth or even less magnetizing power on its core than F has on its core.

Fig. 5 shows the iron tieldirame connecting F and M as provided with projections toward thearmature acting as false poles. They somewhat assist the action of M in opposing the magnetism of F, by permitting lateral diversion of magnet-ism from the armature.

In Fig. 6 there are two cores opposed to F, one only of which is wound with the coil M, while the other, M, serves merely as a conduetor of magnetism, and is made of rather limited section. The presence of M does not prevent theeffect which M has in the structure.

The actions of the machine so constructed are as follows: instead of the machine exhib iting a characteristic curve similar to that of Fig. 7, where the ordinates represent electro-motive forces and the abscissas the currents generated, (which curve is that given by a machine with a strong saturated tield and with an armature with considerable iron and moderate amount of copper winding) itgives a curve more like that of Fig. 8. They differ in these respects. Let the normal current of the machine be ten amperes. Then, in Fig. '7, when ten amperes exist, the curve would indicate about four hundred and seventy-five volts, but at fifteen amperes more nearly five hundred volts. For arc lights such a condition is unstable, because there is in a machine of low internal resistance nothing to limit the current to its normal ten ampcres; but in Fig. S, which shows very nearly the curve of my machine at ten amperes, the volts are, say, three hundred and titty; but should the resistance of the circuit fall so as to bring the current to fifteen amperes, the volts would be less than three hundred. This condition tends to limit the current in are lights to the normal ten, any tendency to surpass it is accompanieiii by a fall of electromotive force of the machine. If the saturated magnet F were alon c acting, the curve of the machi no would approximate that of Fig. 7, and the curve Fig. 8 given is the result of the compounding of that of Fig. 7 with the effect of the opposing coil M on its non-saturated and large core.

The effect of coil M is shown in Fig. 9 by the line 0 0. As it is an opposing coil, its effect is negative, or it tends to cause fall of electrontotive force nearly in proportion to the current in its coils. Thus at ten amperes, Fig. 9, itgivcsa negativeclcctro motive force ot'about one hundred and iifty volts, and at lil'teen amt l l l pores about two hund red volts. The conditions above are assumed; but the effects with other numbers of ampercs an d machines for higher or lower voltage will be similar to the illustration given. In brief, the magnetizing effect of current.- in F soon limits itself by saturating its core, while the opposing effect of same current in coil M does not reach a limit, but goes on accumulating as the current is increased, by virtue of the non-saturation of its core of large size and of its few turns of wire.

Fig. 10 shows how two saturated cores, with coils FF, may be applied to the armatureand the opposing coil M be wound to surround the armature, especially when the core of the latter has a large proportion of iron and the cores in the coils FF are limited in section.-

By suitably altering the number and disposition of the field-magnet cores my invention may be applied to other forms of arnmture, as flat rings, spheres, cylinders, fee.

\Vhat I claim as my invention is 1. Thecombination,with the satu ated fieldmagnet, of a feeble opposing coil wound over a mass of iron inductively acted upon by the saturated magnet, as and for the purpose described.

2. In a dynamo-electric machine or motor, a field-magnet normally maintained by a coil which saturates or a 'iproximately saturates the mass ofiron upon which it is wound, in combination with a weak demagnetizing-coil normally tending to cut down the magnetism or magnetic field developed by the first-named coil and varying in its effect with the current on the circuit, as and for the purpose described.

3. The combination, in a dynamo-electric machine or motor, of a field magnet coil which saturates or approximately saturates its core and a weak demagnetizing-coil wound on a core whose pole isinductively magnetized from the pole of the first-named core.

A In a dynamo-electric machine or motor,

the combination, with the same armature, of

a saturated field'core and a non saturated core wound with a feeble magnetizing-coil which opposes the magnetism induced in its core front the saturated core, as and for the purposedcscribed.

5. In a dynamo-electric machine or motor, the combination of a satinrated and a non-sat urated core diametrically oppositeoncanother and wound with coils in the main circuit.

(5. In a dynamo-electric machine or motor, a lield-magnct maintained solely by the action of a nniin-circuit coil, which saturates its core, in combination with a feeble opposing coil connected into the main circuit.

Signed at Lynn, in the county of Essex and State of Massach usetis, this 24th day of March, A. D. 1887.

ELHIU THOMSON.

\Vitnesses:

i \ViLnUn Rios, Jr., J. W. tirnnonnv.

lCO 

